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The tails may be matched to the fuse.
PME no access
- Thread starter seasickstevie
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wishful thinking !
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Why?
I thought a modern service cable and modern cutout was unlikely to have a 60A fuse.
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My house has one, although the fuseholder is marked "100A"
As I don't have electric heating or an electric shower, my maximum usage falls far below that.
But I do agree that the tails in the pic look surprisingly small.
mine are 25mm², obv.
As I don't have electric heating or an electric shower, my maximum usage falls far below that.
But I do agree that the tails in the pic look surprisingly small.
mine are 25mm², obv.
I may be wrong, but I think that DNOs (or 'the rules to which they work') regard 16mm² tails as adequate for 100A.
In terms of BS7671, the situation is less clear. For some reason, Table 4D1A does not give 'free air' current ratings for (not touching) singles smaller than 25mm². However, looking at 25mm², the free-air CCC is given as 130A is 1.14 times the Method C figure of 114A. If one applies that ratio pro-rata to 16mm² singles (for which they give a CCC of 87A) that would imply a CCC for 'in free air, not touching' 16mm² singles of about 99.18A - hence, 'as near as makes no difference' to being adequate for 100A, even in the eyes of BS7671.
Kind Regards, John
I read one of my years old threads yesterday which said 60A fuse in the max for 16mm (I think, maybe 80a). I think it could of been you who replied.
As I've just written, even if one pays attention only to what is explicitly written in BS7671, then 16mm² singles are adequate with an 80A fuse, since it it gives the Method C CCC as 87A. However, as I said, if one 'estimates' the (missing from BS7671) 'in free-air' CCC for 16mm² singles, then that figures is 'as near to 100A as makes no difference' - so essentially OK with a 100A fuse.
Kind Regards, John
to my eye, the ones in the pic look more like 10mm than 16mm.
But they are downstream of the meter, so they are the consumer's, not the DNO's.
Maybe, but it's always difficult to be sure from photos. In any event, as is often said here, many a flat is supplied with 10mm² cables.
Kind Regards, John
Wrong post
You're correct, they're certainly smaller that 16mm². As the meter terminals are sealed, there's not a lot I can do other than put a Henley block just after the meter, and change up to 25mm², which is what I've done since the picture was taken actually.
It's now down to the smart-meter installer (who'll be along soon no doubt) to shove the 25s into the meter, then it's all covered for future eventualities.
Hard to tell without being there, but to me the outgoing tails look roughly two sizes smaller than the incomers. If the incomers are 25 then 10mm2 out might not be a problem depending on the fuse size, but if the incomers are 16 then it would have to be under a fusing size commonly used by the DNOs to give adequate protection to 6mm2 tails.
Having said that, it's not uncommon to come across 6mm2 tails on small scale E7 installations from 30-40 years ago protected only by a 100a fuse in the cutout, in this part of the country at least. They tend to fuse it down to 60a on smart meter installs currently which, whilst still not ideal, at least brings it a bit more in scope.
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